Indirect calorimeter for medical applications

• US 6,629,934 B2
• Filed: 02/01/2001
• Issued: 10/07/2003
• Est. Priority Date: 02/02/2000
• Status: Expired due to Fees

• Current Assignee: Microlife Medical Home Solutions Inc.
• Original Assignee: HealtheTech, Inc.
• Inventors: Mault, James R., Pearce, Edwin M. Jr.
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): MALLARI, PATRICIA C
• Application Number:
  US09/773,797
• Publication Number:
  US 20010029340A1
• Time in Patent Office: 978 Days
• Field of Search: 600/300-301, 600/529, 600/531, 600/532, 600/538, 604/65-67, 128/202.15, 128/204.23, 128/205.23, 128/204.21, 128/204.22, 128/204.18, 128/204.26, 73/233
• US Class Current: 600/538
• CPC Class Codes: A61B 2560/0295 adapted for recording user messages or annotations
• CPC Class Codes: A61B 2560/0456 Apparatus provided with a docking unit
• CPC Class Codes: A61B 2560/0462 Apparatus with built-in sensors
• CPC Class Codes: A61B 2560/0468 Built-in electrodes
• CPC Class Codes: A61B 2560/0475 Special features of memory means, e.g. removable memory cards
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/0833 Measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• CPC Class Codes: A61B 5/097 Devices for facilitating collection of breath or for directing breath into or through measuring devices
• CPC Class Codes: A61B 5/1112 Global tracking of patients, e.g. by using GPS
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/222 : combined with detection or measurement of physiological parameters, e.g. heart rate
• CPC Class Codes: A61B 5/339 : Displays specially adapted therefor
• CPC Class Codes: A61B 5/4866 : Evaluating metabolism A61B5/083 takes precedence
• CPC Class Codes: A61B 5/4872 : Body fat
• CPC Class Codes: A61B 5/6817 : Ear canal
• CPC Class Codes: A61B 5/6826 : Finger
• CPC Class Codes: A61B 5/6838 : Clamps or clips
• CPC Class Codes: A61B 5/6896 : Toys
• CPC Class Codes: A61B 5/742 : using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 7/00 : Instruments for auscultation
• CPC Class Codes: A61M 16/0051 : with alarm devices
• CPC Class Codes: A61M 16/024 : including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/08 : Bellows; Connecting tubes having means for taking samples G01N1/22; Water traps; Patient circuits
• CPC Class Codes: A61M 2016/0036 : in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2202/0275 : Nitric oxide [NO]
• CPC Class Codes: A61M 2205/3569 : sublocal, e.g. between console and disposable
• CPC Class Codes: A61M 2205/3584 : using modem, internet or bluetooth
• CPC Class Codes: A61M 2205/3592 : using telemetric means, e.g. radio or optical transmission
• CPC Class Codes: A61M 2205/52 : with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2209/086 : Docking stations
• CPC Class Codes: A61M 2230/43 : Composition of exhalation
• CPC Class Codes: A61M 2230/432 : partial CO2 pressure (P-CO2)
• CPC Class Codes: A61M 2230/435 : partial O2 pressure (P-O2)
• CPC Class Codes: G01F 1/662 : Constructional details
• CPC Class Codes: G01N 2291/02809 : Concentration of a compound, e.g. measured by a surface mass change
• CPC Class Codes: G01N 2291/02818 : Density, viscosity
• CPC Class Codes: G01N 2291/02836 : Flow rate, liquid level
• CPC Class Codes: G01N 29/024 : by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 33/497 : of gaseous biological material, e.g. breath

Abstract

An improved respiratory analyzer comprises a disposable flow module and non-disposable electronics module. An improved ventilator system comprises a supply of respiratory gases, a ventilator line for directing the respiratory gases to a patient, a flow module holder located in series with the ventilator line into which a flow module can be inserted, and an electronics module which connects to the flow module. In a preferred embodiment, the flow module and electronics module operate in combination to provide the functionality of an indirect calorimeter, so as to determine the metabolic rate of the patient. Feeding of an intubated patient can be controlled using determined patient metabolic rates. Other respiratory parameters can be determined by the system, such as peak flow, tidal volume, end-tidal concentrations, and respiratory quotient. The system provides a non-invasive method of cardiac output determination. A flow module can also be inserted into the mouth or internal respiratory tube of a person.

Claims

1. A ventilator system for assisting a patient in breathing comprising:

a supply of inhalation respiratory gases;

a respiratory conduit providing a flow pathway for an inhalation and exhalation respiratory gas flowing therethrough between said supply of inhalation respiratory gases and the patient;

a valve disposed within said respiratory conduit for controlling the flow of inhalation and exhalation respiratory gases;

a flow module holder located within the conduit between said valve and the patient; and

a respiratory gas analyzer located between said valve and the patient, the analyzer comprising;

a flow module, adapted to be placed within the flow module holder in the conduit, so that the inhalation and exhalation respiratory gases pass through a flow path of the flow module, the flow module containing a flow rate sensor disposed in the flow path of the flow module for determining a flow rate of the inhalation and exhalation respiratory gases, and

an electronics module, adapted to be integrally connected to the flow module, and adapted to calculate a respiratory parameter using the determined flow rate of the inhalation and exhalation respiratory gases flowing through the flow path.

2. The ventilator system of claim 1, wherein the supply of respiratory gas is a mechanical ventilator.

3. The ventilator system of claim 1, wherein the flow sensor comprises a pair of ultrasonic transducers operable so as to provide a signal correlated with flow rate through the flow path.

4. The ventilator system of claim 1 wherein the flow module includes a generally cylindrical housing, an ultrasonic transducer transmitting and receiving ultrasonic pulses along a path oblique to the flow of inhalation and exhalation respiratory gas in the flow path, a pathogen-resistant liner lining an inside surface of the housing to protect the ultrasonic transducer and a gas component concentration sensor disposed in the flow path from contamination due to the flow of inhalation and exhalation respiratory gas, wherein the liner is replaceable.

5. The ventilator system of claim 1, wherein the electronics module is adapted to calculate a metabolic rate of the patient.

6. The ventilator system of claim 1 wherein the flow module is disposable and the electronics module is non-disposable, and the flow module is removably mounted to the electronics module.

7. The ventilator system of claim 1 wherein the flow module includes a housing enclosing the flow path, and the flow sensor is mounted in the flow path on the housing.

8. A ventilator system adapted to be placed in fluid communication with an airway of a patient comprising:

a supply of inhalation respiratory gas;

a respiratory conduit providing a flow pathway for an inhalation and exhalation respiratory gas flowing therethrough;

an inlet conduit operatively connected between the supply of respiratory gas and the respiratory conduit for directing an inhalation respiratory gas to the patient;

a return conduit operatively connected between the supply of inhalation respiratory gas and the ventilator, for returning exhalation respiratory gas to the supply of respiratory gas;

a valve disposed between the inlet conduit, respiratory conduit and outlet conduit for controlling the flow of gas to each of the conduits;

a respiratory gas analyzer operatively positioned in the patient'"'"'s airway, wherein the respiratory gas analyzer includes a disposable flow module having a flow path operatively connected to a non-disposable electronics module;

an ultrasonic flow sensor in fluid communication with the flow path for detecting gas flow volume in the flow path; and

a gas component sensor in fluid communication with the flow path for detecting gas component concentration levels in the flow path, wherein the electronics module uses the gas flow volume and gas component concentration level to determine a metabolic rate of the patient.

9. The ventilator system of claim 8 wherein the flow module is operatively connected to the electronics module using a wireless communications link.

10. The ventilator system of claim 8 wherein the flow module is operatively connected to the electronics module using a wired communications link.

11. The ventilator system of claim 8 wherein the flow module includes a housing enclosing the flow path, and the flow sensor is mounted in the flow path on the housing.

12. The ventilator system of claim 8 wherein the gas component sensor is an oxygen sensor in fluid communication with the flow path for determining an oxygen concentration level of the respiratory gas flowing through the flow path.

13. The ventilator system of claim 8 wherein the gas component sensor is a carbon dioxide sensor in fluid communication with the flow path for determining the level of carbon dioxide of the respiratory gas flowing through the flow path.

14. The ventilator system of claim 8 wherein the electronics module includes a housing, a circuit board disposed within the housing, a transducer interface and a transducer connector for communicating with the flow sensor and the gas component sensor, a processor, memory and a display.

15. The ventilator system of claim 8 wherein generally cylindrical housing, ultrasonic transducers transmitting and receiving ultrasonic pulses along a path oblique to the flow of respiratory gas in the flow path, a pathogen-resistant liner lining an inside surface of the housing to protect the ultrasonic transducer and gas component concentration sensor from contamination due to the flow of respiratory gas, wherein the liner is replaceable.

16. A system for providing intravenous feeding to a person connected to a ventilator, the method comprising:

a ventilator system, having a holder adapted to receive a flow module;

an indirect calorimeter, comprising a non-disposable electronics module and a disposable flow module, the flow module enclosing a flow path, the flow module being placed within the holder of the ventilator system so that gases respired by the person pass through the flow path;

an intravenous feeding unit, the unit comprising a source of intravenous food, a delivery tube for delivering the food to the person, and a pump adapted to pump intravenous food from the source along the delivery tube at a controlled pump rate; and

a communications link between the indirect calorimeter and the infusion pump, so as to modify the controlled pump rate of food to the person according to data provided by the indirect calorimeter.

17. A ventilator system adapted to be placed in fluid communication with an airway of a patient comprising:

a supply of inhalation respiratory gases;

a respiratory conduit providing a flow pathway for an inhalation and exhalation respiratory gas flowing therethrough;

a flow module holder located within the conduit; and

a respiratory gas analyzer, the analyzer comprising;

a flow module, adapted to be placed within the flow module holder in the conduit, so that the inhalation and exhalation respiratory gases pass through a flow path of the flow module, the flow module containing a flow rate sensor for determining a flow rate of the inhalation and exhalation respiratory gases, wherein the flow module is disposed in the airway of the patient and includes a generally cylindrical housing enclosing the flow path, a pair of ultrasonic transducers positioned to transmit and receive ultrasonic pulses along a direction having a direction component along the flow path, a flexible tube disposed between the flow module and a valve unit, and a capnometer in the exhalation conduit for measuring a volume of carbon dioxide in the exhaled respiratory gas, and

an electronics module, adapted to be connected to the flow module, and adapted to calculate a respiratory parameter using the determined flow rate of the inhalation and exhalation respiratory gases flowing through the flow path.

18. A ventilator system for assisting a patient in breathing comprising:

a supply of inhalation respiratory gases;

a respiratory conduit providing a flow pathway for an inhalation and exhalation respiratory gas flowing therethrough between said supply of inhalation respiratory gases and the patient;

a valve disposed within said respiratory conduit for controlling the flow of inhalation and exhalation respiratory gases;

a flow module holder located within the conduit between said valve and the patient;

a gas component sensor, sensitive to a respiratory gas component, operable so as to provide a signal correlated with an instantaneous concentration of a respiratory gas component; and

a respiratory gas analyzer located between said valve and the patient, the analyzer comprising;

a flow module, adapted to be placed within the flow module holder in the conduit, so that the inhalation and exhalation respiratory gases pass through a flow path of the flow module, the flow module containing a flow rate sensor disposed in the flow path of the flow module for determining a flow rate of the inhalation and exhalation respiratory gases, and

an electronics module, adapted to be integrally connected to the flow module, and adapted to calculate a respiratory parameter using the determined flow rate of the inhalation and exhalation respiratory gases flowing through the flow path.

19. The ventilator system of claim 18 further comprising a gas component sensor, wherein the gas component sensor is an oxygen sensor analysis module having a housing, an electronics circuit, an excitation radiation source, a sensing channel optical detector, a reference channel optical detector and external connection, such that the oxygen sensor analysis module is disposed within an indentation of a housing for the flow module having a sensing channel fluorescent film and reference channel fluorescent film on its inner surface, and the surface of the sensing channel film is exposed to the inhalation and exhalation respiratory gas flow and the reference channel film is protected from the oxygen in the inhalation and exhalation respiratory gas flow by an oxygen-impermeable film, and a transparent wave guide film for optical coupling between the oxygen sensor analysis module and the fluorescent film, for measuring oxygen consumption by the patient.

20. The ventilator system of claim 18 further comprising a gas component sensor disposed in the flow module, wherein the gas component concentration sensor measures the concentration of nitric oxide in the inhaled respiratory gas.

21. The ventilator system of claim 18 further comprising a gas component sensor disposed in the flow module, wherein the gas component concentration sensor measures the concentration of gas components in the exhaled respiratory gas.

22. The ventilator system of claim 18 further comprising a gas component sensor disposed in the flow module, wherein the gas component sensor is an oxygen sensor in fluid communication with the flow path for determining an oxygen concentration level of the inhalation and exhalation respiratory gas flowing through the flow path.

23. The ventilator system of claim 18 further comprising a gas component sensor disposed in the flow module, wherein the gas component sensor is a carbon dioxide sensor in fluid communication with the flow path for determining a level of carbon dioxide of the inhalation and exhalation respiratory gas flowing through the flow path.

24. The ventilator system of claim 18 wherein the flow module holder is a connecting means.

25. The ventilator system of claim 24 wherein the connecting means is a connector and a collar.

26. The ventilator system of claim 18 wherein the flow module includes an inlet portion connected to a first lateral offset portion, that is connected to a central portion, that is connected to a second lateral offset portion, and also connected to an outlet portion.

27. The ventilator system of claim 18 wherein the electronics module includes a housing, a circuit board disposed within the housing, a transducer interface and a transducer connector for communicating with the flow sensor, a processor, a memory and a display.

28. The ventilator system of claim 27 wherein the electronics module includes a micromachined ultrasonic transducer containing an array of micromachined temperature, pressure and humidity sensing elements.

29. The ventilator system of claim 18 wherein the flow sensor and the gas component sensor are disposed in the flow path of the flow module, and the flow module is connected to the electronics module using a wireless communications link.

30. The ventilator system of claim 18 wherein the flow module includes a housing enclosing the flow path formed by a first chamber, a central flow path and a second chamber, such that the first chamber and second chamber are separated by a partition to provide a coaxial flow geometry of the respiratory gas.

31. The ventilator system of claim 18 wherein the flow module includes a housing enclosing the flow path formed by a first chamber, a central flow path formed by a circular flow tube, a second chamber, and a partition separating the first and second chambers, such that a direction of the inhalation and exhalation respiratory gas flow in the central flow path is perpendicular to a flow direction of inhaled respiratory gas.

32. The ventilator system of claim 18 wherein the flow module includes a housing enclosing a ventilator-side chamber, a central flow path formed by a flow tube, a patient-side chamber, and a partition separating the ventilator-side and patient-side chambers.

33. The ventilator system of claim 18 wherein the flow module includes a housing surrounding a central flow path, a recess formed within an inside surface of the housing for supporting an ultrasonic transducer within the flow path, an oxygen sensor positioned to sense the inhalation and exhalation respiratory gas flow along the central flow path, and an interface unit for transferring a signal between the ultrasonic transducer, and oxygen sensor and electronics module.

34. The ventilator system of claim 18 wherein the flow module includes a housing having a generally cylindrical shape surrounding a flow path, a strut within the housing for supporting an ultrasonic transducer within the flow path, an oxygen sensor positioned to sense the respiratory gas flow along the flow path, and an interface unit for transferring a signal between the ultrasonic transducer, and oxygen sensor and electronics module.

35. The ventilator system of claim 18 wherein the flow module includes a housing having a generally cylindrical shape surrounding a central flow path, an ultrasonic transducer within the flow path, an indentation in a top surface of the housing for receiving an external oxygen sensor that is removable from the flow module, and an interface unit for transferring a signal between the ultrasonic transducers, oxygen sensor and electronics module.

36. The ventilator system of claim 18 wherein the flow module includes a housing having an oxygen sensitive fluorescent coating on an inner surface of the housing, a transparent membrane separating the fluorescent coating from an external radiation source and detector, wherein an optical fiber conveys excitation radiation to the fluorescent coating and fluorescent radiation from the fluorescent coating returns along the optical fiber.